1. Field of the Invention
This invention relates to curable silicone pressure sensitive adhesive tape useful for bonding in structural applications.
2. Background Information
Many methods of using adhesives for bonding the various components of buildings together have been developed. Adhesives have been used in the manufacture and attachment of exterior panels in curtain walls, such as in structural glazing systems.
A system for use in structural glazing has been developed in which an adhesive sealent has been used to bond the glass exterior panel to the curtain wall frame and to seal the joint formed. A discussion of such a system is found in "The Role of Adhesive Sealants in Structural Glazing", Architects's Guide to Glass, Metal & Glazing, Annual Edition, 1985, p 48-54. The system discussed makes use of silicone sealants which bond curtainwall components together. The components must be held in place while the silicone sealant cures to an elastomeric material from the paste material it is at the time of application.
A variation of the above system is described in "Sealants in Construction", Klosowski, Marcel Deker, Inc, New York, N.Y., 1989, at page 248. The backing material used to form the joint between metal frame and glass curtain in a factory during construction of the assembly is a urethane foam tape. This foam tape has a pressure sensitive adhesive on two sides. The tape is applied to the frame as a gasket, then the glass placed over it. The adhesive holds the glass in place while a silicone sealant is installed between the frame and glass and allowed to cure, to permanently bond the two pieces together.
Another system has been developed in Japan which uses a thin layer of silicone sealant to bond the glass sheet to a silicone rubber gasket, which is in turn secured by a metal holder which is bolted to the structural part of a building to attach the glass curtain to the building. The gasket is bonded to the glass in a factory, as the assembly must have several days to cure and bond before it is attached to the building.
A glazed impervious sheet assembly and method of glazing are described in U.S. Pat. No. 3,881,290, issued May 6, 1975. The method makes use of a pressure sensitive resilient tape to seal between an exterior stop and the impervious sheet. Shown is a suitable polyvinyl chloride foam ribbon and silicone pressure sensitive adhesive useful in the method.
Glass butt joints for curtain wall construction are taught in U.S. Pat. No. 4,912,898, issued Apr. 3, 1990. The construction uses an insulating panel unit made up of two parallel sheets which are separated by use of a spacer and bonded together by a sealing means, such as polysulphide, butyl, and silicone compounds. Metal brackets are factory attached to the insulating panel unit with sealant, which is cured before installation of the panels into the building. After installation, a sealant is used to seal the space between units.
None of the above described systems can be used to bond two surfaces together through the use of a pressure sensitive adhesive with sufficient long term integrity so that support brackets are not necessary either during assembly or during use.
A pressure sensitive adhesive tape is described in U.S. Pat. No. 4,396,675, issued Aug. 2, 1983. The tape is applied to a surface and is then heated to crosslink the adhesive. The crosslinked adhesive exhibits excellent resistance to common organic solvents and exceptional resistance to shear failure, especially at elevated temperatures.
A method of bonding surfaces with a permanent-bond adhesive is taught in U.S. Pat. No. 4,613,534, issued Sep. 23, 1986. The method bonds surfaces coated with elastoplastic organopolysiloxane resin or polytertrafluoroethylene resin. The adhesive is a multi-part composition which cures when the parts are mixed together and the solvent is removed. The adhesive does not make a pressure sensitive adhesive.
When pressure sensitive adhesives are used as tapes, they are commonly protected when formed into rolls with a releasable liner which has a coating which does not adhere to the pressure sensitive adhesive. A coating composition which is useful in this manner is described in U.S. Pat. No. 4,736,048, issued Apr. 5, 1988, while the method of coating this composition to make such a releasable liner is claimed in U.S. Pat. No. 4,842,902, issued Jun. 27, 1989. U.S. Pat. No. 4,889,753, issued Dec. 26, 1989, claims a releasable liner and a laminate of the liner and pressure sensitive adhesive. Another such composition is described in U.S. Pat. No. 4,980,440, issued Dec. 25, 1990. This composition is stated to have a faster curing time and a longer bath life.
In co-pending applications for U.S. patent, titled "SOLUTION-STABLE, MOISTURE-CURABLE SILICONE PRESSURE SENSITIVE ADHESIVES", U.S. patent application Ser. No. 07/748,477, and "STABLE, MOISTURE-CURABLE SILICONE PRESSURE SENSITIVE ADHESIVES", U.S. patent application Ser. No. 07/748,500 filed on even date herewith and assigned to the assignee of this application, there are disclosed and claimed moisture-curable silicone pressure sensitive adhesive (SPSA) compositions. The use of these SPSA compositions would be greatly enhanced if they could be protected in thin film form with a release liner. The disclosures of said co-pending and co-assigned applications are incorporated herein by reference to fully delineate these SPSA compositions and how to prepare them.
Tangney, U.S. Ser. No. 276,178, filed on Nov. 23, 1988 and assigned to the assignee of this application disclosed a laminate article comprising a fluorosilicone release liner and an addition-cured SPSA.